The chairman of the committee, Liam Twomey, has told the Irish Mortgage Holders Organisation (IMHO) that it shares "serious concerns" over the lender's routine overcharging of customers who were denied cheaper tracker mortgages.

He said the subject of PTSB was added to the committee's programme at its first meeting since the Dail resumed. The IMHO has called for Permanent TSB to be held to account publicly over the tracker-mortgage scandal to ensure that it was dealing fairly with customers.

David Hall, director of the IMHO, has also asked the committee to hear testimony in private from customers who were overcharged by PTSB.

He said: "We have over 100 clients who are directly affected and whom we are assisting. Their stories are horrific and have not been heard."

The Oireachtas committee has also written to the Central Bank to back the IMHO's call for an investigation across all banks that sold tracker products.

Meanwhile, David Hall has confirmed that the Central Bank is sending investigators to the IMHO's offices next month to examine the files of clients who believe that they were denied a tracker mortgage by other banks, including Allied Irish Banks.

As revealed in the Sunday Independent last month, AIB has given tracker mortgages and, in some cases, some compensation or even a debt writedown to some customers who complained that they should have been put on a tracker, although the bank has not admitted any wrongdoing.

The committee hearing will be the first public forum on the tracker-mortgage scandal since the Central Bank published its scathing report on Permanent TSB.

It found that 1,372 customers were entitled to tracker mortgages but the bank made them pay much higher standard variable rates.

The bank has promised refunds of the amounts overcharged, compensation and up-front payments of €50,000 and €25,000 to 61 people who lost homes or properties as a result.

David Hall said a further complication had arisen for four customers who have lost their homes and are going through bankruptcy as a result of their mortgage debt. He accused the bank of unnecessarily prolonging their periods in bankruptcy.

Bankrupts are required by law to surrender their finances to their bankruptcy supervisor, which means they will first have to be released from bankruptcy in order to claim the compensation for losing their home. However, they can only exit the process with the permission of their main creditor, which, in most of these cases, is Permanent TSB.

According to Mr Hall, Permanent TSB's position was that the bankrupt customers would have to go through the independent appeals panel first for approval, a process that could take 40 days.

In a letter to the Central Bank, he wrote: "Effectively this means these individuals, currently subject to bankruptcy restrictions, face unnecessary time as a bankrupt.

"We have a number of clients who are currently stuck in a bankruptcy process that they should not be.

"Their lives are restricted by the powers of the Official Assignee, including what they can live on and where their children can go to school."